Field of the Invention
The disclosure relates generally to methods and devices for mitigating switching noise from power management integrated circuits, and more particularly it relates to methods and devices for adjusting phase delays among at least two switched-mode DC-DC power converters.
Description of the Related Art
Switched-mode DC-DC converters are important in portable electronic devices such as cellular phones and laptop computers, which are supplied with power primarily from batteries. Such electronic devices often contain several sub-circuits, each with its own voltage level requirement that is different from that supplied by the battery or an external supply (sometimes higher or lower than the supply voltage). Additionally, the battery voltage declines as its stored energy is drained. Switched-mode DC-DC converters offer a method to increase voltage from a partially lowered battery voltage thereby saving space instead of using multiple batteries to accomplish the same thing. Most switched-mode DC-DC converters also regulate the output voltage.
Electronic switched-mode DC-DC converters convert one DC voltage level to another by storing the input energy temporarily and then releasing that energy to the output at a different voltage. The storage may be in either magnetic field storage components (inductors, transformers) or electric field storage components (capacitors). This conversion method is more power efficient (often 75% to 98%) than linear voltage regulation (which dissipates unwanted power as heat). This efficiency is beneficial to increasing the running time of battery-operated devices. The efficiency has increased since the late 1980s due to the use of power FETs, which are able to switch at high frequency more efficiently than power bipolar transistors, which incur more switching losses and require a more complicated drive circuit. Another important innovation in switched-mode DC-DC converters is the use of synchronous rectification replacing the flywheel diode with a power FET with low “on-resistance”, thereby reducing switching losses.
Most switched-mode DC-DC converters are designed to move power in only one direction, from the input to the output. However, all switching regulator topologies can be made bi-directional by replacing all diodes with independently controlled active rectification. A bi-directional converter can move power in either direction, which is useful in applications requiring regenerative braking Switched-mode DC-DC converters are now available as integrated circuits needing minimal additional components. They are also available as a complete hybrid circuit component, ready for use within an electronic assembly.
However, each switched-mode DC-DC converter works with a clock signal, such that discontinuous current occurs at the output node. That is, switched-mode DC-DC converters generate switching spurs at the output node. The sensitive circuits, such as RF transceiver circuits, suffer interference issues from the switching spurs. For the sake of mitigating interference, which is generated by the switched-mode DC-DC converters, to the sensitive circuits, devices and methods for effectively mitigating the switching spurs are necessarily required.